Biginelli reaction under chemically friendly and in parallel conditions: a practical class of organic synthesis for medicinal chemistry, chemistry and pharmacy courses

Green chemistry is a goal pursued by synthetic chemists in the development of environmentally friendly and sustainable protocols. The combination of a multicomponent reaction with parallel synthesis is a very efficient and green strategy aiming to generate structurally diverse products in a short time. The practical one-pot multicomponent synthesis of a small library of twelve dihydropyrimidinones (DHPM) using parallel synthesis is reported here as an undergraduate experiment for the organic synthesis laboratory. This protocol employed triethyl orthoformate (TEOF) as the promoter of the reaction in solvent-free conditions and using microwave as an energy source, which is in agreement with green chemistry goals. The products were isolated through precipitation in water and purified by recrystallization when necessary. The students also carried out, through a directed study, the structural analysis of their compounds by melting point determination, infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy. (author)